Same issue here.
I think this happens when a major stable update. The ads work perfectly before that.
In my case, the game will be stuck / blank when opened with an internet connection. but when I turn it off before running and turn it on again when the game is already loaded/running, it works.
I also do some logging in the phone (just simply put alert("")), to test the ads are configured or not, and the alert popped up!.
So I think it's only stuck at first time load (after the splash screen)